This invention is directed to a continuous mining apparatus and method for the underground mining of coal from seams.
In underground coal mining a shaft, hole or tunnel is usually excavated to the coal seam. The miners then develop horizontal entries through the seam of coal so that the coal is mined through tunnels spreading out from the shaft, hole or tunnel. Elevators or other conveying means are used to lower or raise miners and equipment between the mine entrance at the surface and the level of the coal. Similarly, elevators or handling devices lift or convey the coal out of the mine.
The principal method of mining coal today employs a continuous miner which bites into the face of the coal seam and causes the coal to pass from the front of the machine to the rear thereof where it flows into shuttle cars or onto a conveyor belt. The continuous miner operates at the working face of the mine and eliminates separate cutting, drilling, blasting and loading operations called for in conventional mining.
At the working face of the mine roof control methods are used in order to reinforce the roof and prevent its collapse during mining. One popular method of roof control involves the use of mine roof bolts and bearing plates. Such bolts are positioned in holes drilled into the mine roof. When tightened the mine roof bolt functions with the associated bearing plate as a clamp to hold the rock strata together to thus minimize the possibility of a roof fall.
In order to hold the mine roof bolt in place in the mine roof it is necessary to provide for some sort of anchorage system. Various devices are in use including mechanical expansion type anchors or shells and resin anchors, just to name a few.
The placement of mine roof bolts in an underground mine is time consuming. The precise locations of the bolts in the mine roof are set out in an approved roof control plan issued by the U.S. Department of the Interior, Mining Enforcement and Safety Administration. Each mine has its own mine roof control plan depending upon local conditions.
A typical mine roof control plan will call for the placement of mine roof bolts as a part of roof control at approximately five foot centers in the mine roof. Typical plans also provide that in mining the cut, the continuous mining machine shall not be advanced past the last row of permanent supports (bolts) until additional mine roof bolts have been put in place. Typically, only persons engaged in installing temporary supports or mine roof bolts are allowed to proceed beyond the last row of permanent supports or bolts. When installing supports or bolts in the face area typical plans permit workmen to be positioned not more than five feet from a temporary or permanent support.
Roof control methods including the placement of mine roof bolts thus limit the extent to which a continuous miner may operate in mining a cut. In some cases, the continuous miner is permitted to advance only approximately ten feet into the coal face before it must be withdrawn in order to permit miners to install roof support systems.
As a consequence, therefore, of the implementation of safety standards involving mine roof control the continuous miner operates for only relatively short periods of time before roof control measures have to be installed. This necessitates a great deal of movement of the continuous miner from place to place as cuts are made and roof bolts are installed. It is not uncommon in an eight hour shift to experience only two hours of continuous miner operation with the remaining six hours of the shift devoted to movement of the continuous miner and roof control procedures such as bolting.
This invention contemplates a continuous miner and method in which relatively long cuts are made in a coal face (on the order of 80-100 feet) and in which it is not necessary for a miner to work in an unsupported area of the mine. More particularly, this invention contemplates the use of a continuous mining apparatus in which the cutter assembly of the miner can be remotely advanced into the coal face for relatively long distances to enable relatively large amounts of coal to be removed from the seam without the necessity of stopping the miner and moving it to another location to permit mine roof control procedures to be put in place. Rather, applicant's apparatus and method contemplates the taking of relatively long cuts in the seam and the removal of the continuous miner to another location while mine roof control procedures are implemented in the relatively long cut just made.